CN110759807A - Preparation method of p-fluorotoluene - Google Patents
Preparation method of p-fluorotoluene Download PDFInfo
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- CN110759807A CN110759807A CN201911020640.8A CN201911020640A CN110759807A CN 110759807 A CN110759807 A CN 110759807A CN 201911020640 A CN201911020640 A CN 201911020640A CN 110759807 A CN110759807 A CN 110759807A
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- temperature
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- fluorotoluene
- toluidine
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/093—Preparation of halogenated hydrocarbons by replacement by halogens
Abstract
The invention discloses a preparation method of p-fluorotoluene, which comprises the following steps: reducing the anhydrous hydrogen fluoride to 0-5 ℃, slowly dropwise adding p-toluidine at the temperature of not more than 20 ℃, adding sodium nitrite after the dissolution is finished, and keeping the temperature at 0-5 ℃ for 1 h; then entering a pyrolysis stage; after pyrolysis, preserving heat for 2-3h, cooling, separating out an organic phase, and neutralizing with sodium carbonate until the pH is = 7-8; distilling to obtain p-fluorotoluene; the pyrolysis is divided into 4 stages. The preparation method is simple and easy to operate, and by precisely controlling the temperature and time in the four pyrolysis stages, the side reactions and the generation of byproducts are obviously reduced; the method has simple raw materials, does not need to spend large energy consumption, and saves the cost; the purity of the p-fluorotoluene prepared by the method can reach more than 99.4 percent, and the yield can also reach more than 97 percent.
Description
Technical Field
The invention belongs to the technical field of chemical industry, and particularly relates to a preparation method of p-fluorotoluene.
Background
The p-fluorotoluene is an important organic fluorine compound raw material and is used for synthesizing various medicines, pesticides, dyes, high-molecular fluoroplastic intermediates and fluorine-containing aromatic derivatives. At present, p-fluorotoluene is also prepared by an indirect method, and the fluorination method mainly comprises the following steps: diazotization fluorination of toluidine (Hieman reaction), halogen exchange, catalytic halogenation and fluorination with special fluorinating agents. Among them, diazotization fluorination has been studied more. In addition to the conventional production process of the schieman reaction, p-toluidine is subjected to diazotization and fluorination reaction in anhydrous hydrogen fluoride containing ammonium ions, and the generated diazonium fluoroborate is decomposed in a solution to obtain a product.
However, the preparation method of p-fluorotoluene in the prior art has the problems of more side reactions and low purity and yield of the product.
Disclosure of Invention
In order to solve the technical problem, the invention provides a preparation method of p-fluorotoluene, which comprises the following steps:
reducing the anhydrous hydrogen fluoride to 0-5 ℃, slowly dropwise adding p-toluidine at the temperature of not more than 20 ℃, adding sodium nitrite after the dissolution is finished, and keeping the temperature at 0-5 ℃ for 1 h; then entering a pyrolysis stage; after pyrolysis, preserving heat for 2-3h, then cooling, separating out an organic phase, and then neutralizing with sodium carbonate until the pH value is 7-8; distilling to obtain p-fluorotoluene;
the pyrolysis is divided into 4 stages: heating to 20 ℃ in one section, and keeping the temperature for 4-5 h; heating to 30-35 ℃ in the second stage, and preserving heat for 3-4 h; heating to 40-43 deg.C in three stages, and keeping the temperature for 4-5 h; and heating to 50-55 ℃ in the fourth section, and preserving heat for 2-3 h.
The temperature of the first pyrolysis stage is preferably raised to 20 ℃, and the temperature is kept for 5 hours.
The temperature of the second pyrolysis stage is preferably raised to 30 ℃, and the temperature is kept for 3 h.
The temperature of the three pyrolysis sections is preferably raised to 42 ℃, and the temperature is kept for 5 h.
The temperature of the four pyrolysis stages is preferably raised to 55 ℃, and the temperature is kept for 3 h.
The mass ratio of the p-toluidine to the anhydrous hydrogen fluoride is 1 (2.8-3), preferably 1: 3.
The mass ratio of the sodium nitrite to the p-toluidine is (0.6-0.8): 1, preferably 0.7: 1.
The temperature for cooling is 10-20 ℃.
In the liquid separation process, at least two times of liquid separation are required.
Compared with the prior art, the invention has the beneficial effects that:
(1) the preparation method is simple and easy to operate, and by precisely controlling the temperature and time of the four pyrolysis stages, the side reactions and the generation of byproducts are obviously reduced.
(2) The method has the advantages of simple raw materials, no need of high cost and energy consumption, and cost saving.
(3) The purity of the p-fluorotoluene prepared by the method can reach more than 99.4 percent, and the yield can also reach more than 97 percent.
Detailed Description
A preparation method of p-fluorotoluene comprises the following steps:
reducing the anhydrous hydrogen fluoride to 0-5 ℃, slowly dropwise adding p-toluidine at the temperature of not more than 20 ℃, adding sodium nitrite after the dissolution is finished, and keeping the temperature at 0-5 ℃ for 1 h; then entering a pyrolysis stage; after pyrolysis, preserving heat for 2-3h, then cooling, separating out an organic phase, and then neutralizing with sodium carbonate until the pH value is 7-8; distilling to obtain p-fluorotoluene;
the pyrolysis is divided into 4 stages: heating to 20 ℃ in one section, and keeping the temperature for 4-5 h; heating to 30-35 ℃ in the second stage, and preserving heat for 3-4 h; heating to 40-43 deg.C in three stages, and keeping the temperature for 4-5 h; and heating to 50-55 ℃ in the fourth section, and preserving heat for 2-3 h.
The temperature of the first pyrolysis stage is preferably raised to 20 ℃, and the temperature is kept for 5 hours.
The temperature of the second pyrolysis stage is preferably raised to 30 ℃, and the temperature is kept for 3 h.
The temperature of the three pyrolysis sections is preferably raised to 42 ℃, and the temperature is kept for 5 h.
The temperature of the four pyrolysis stages is preferably raised to 55 ℃, and the temperature is kept for 3 h.
The mass ratio of the p-toluidine to the anhydrous hydrogen fluoride is 1 (2.8-3), preferably 1: 3.
The mass ratio of the sodium nitrite to the p-toluidine is (0.6-0.8): 1, preferably 0.7: 1.
The temperature for cooling is 10-20 ℃.
In the liquid separation process, at least two times of liquid separation are required.
Example 1
Reducing anhydrous hydrogen fluoride to 0 ℃, slowly dripping p-toluidine, keeping the temperature not more than 20 ℃, adding sodium nitrite after dissolution is finished, and keeping the temperature at 0-5 ℃ for 1 h; then entering a pyrolysis stage; after pyrolysis, preserving heat for 2h, then cooling, separating liquid for two times to obtain an organic phase, and then neutralizing with sodium carbonate until the pH value is 7; distilling to obtain p-fluorotoluene;
the pyrolysis is divided into 4 stages: heating to 20 ℃ in one section, and keeping the temperature for 4 hours; heating the second stage to 30 ℃, and preserving the heat for 3 hours; heating the third section to 40 ℃, and preserving heat for 4 hours; and raising the temperature to 50 ℃ in the fourth section, and keeping the temperature for 2 hours.
The mass ratio of the p-toluidine to the anhydrous hydrogen fluoride is 1: 2.8.
The mass ratio of the sodium nitrite to the p-toluidine is 0.6: 1.
the temperature for cooling is 10-20 ℃.
The purity of the p-fluorotoluene prepared by the method can reach 99 percent, and the yield can reach 97 percent.
Example 2
Reducing anhydrous hydrogen fluoride to 0 ℃, slowly dropwise adding p-toluidine at the temperature of not more than 20 ℃, adding sodium nitrite after dissolution is finished, and keeping the temperature at 0 ℃ for 1 h; then entering a pyrolysis stage; after pyrolysis, preserving heat for 3h, then cooling, separating liquid for two times to obtain an organic phase, and then neutralizing with sodium carbonate until the pH value is 7.5; distilling to obtain p-fluorotoluene;
the pyrolysis is divided into 4 stages: heating to 20 ℃ in one section, and keeping the temperature for 5 hours; heating the second stage to 30 ℃, and preserving the heat for 3 hours; heating the third section to 42 ℃, and preserving the heat for 5 hours; and raising the temperature to 55 ℃ in the fourth section, and keeping the temperature for 3 hours.
The mass ratio of the p-toluidine to the anhydrous hydrogen fluoride is 1: 3.
The mass ratio of the sodium nitrite to the p-toluidine is 0.7: 1.
The temperature for cooling is 10-20 ℃.
The purity of the p-fluorotoluene prepared by the method can reach 99.4%, and the yield can reach 97.6%.
Example 3
Reducing anhydrous hydrogen fluoride to 0 ℃, slowly dropwise adding p-toluidine at the temperature of not more than 20 ℃, adding sodium nitrite after dissolution is finished, and keeping the temperature at 0 ℃ for 1 h; then entering a pyrolysis stage; after pyrolysis, preserving heat for 2h, then cooling, separating liquid for two times to obtain an organic phase, and then neutralizing with sodium carbonate until the pH value is 8; distilling to obtain p-fluorotoluene;
the pyrolysis is divided into 4 stages: heating to 20 ℃ in one section, and keeping the temperature for 4 hours; heating the second stage to 35 ℃, and keeping the temperature for 4 hours; heating the third section to 43 ℃, and preserving heat for 4.5 h; and raising the temperature to 52 ℃ in the fourth section, and keeping the temperature for 2 hours.
The mass ratio of the p-toluidine to the anhydrous hydrogen fluoride is 1: 2.9.
The mass ratio of the sodium nitrite to the p-toluidine is 0.8: 1.
the temperature for cooling is 10-20 ℃.
The purity of the p-fluorotoluene prepared by the method can reach 98.8 percent, and the yield can reach 97 percent.
Example 4
Reducing the anhydrous hydrogen fluoride to 5 ℃, slowly dropwise adding p-toluidine at the temperature of not more than 20 ℃, adding sodium nitrite after the dissolution is finished, and keeping the temperature at 5 ℃ for 1 h; then entering a pyrolysis stage; after pyrolysis, preserving heat for 3h, then cooling, separating liquid for three times to obtain an organic phase, and then neutralizing with sodium carbonate until the pH value is 7.5; distilling to obtain p-fluorotoluene;
the pyrolysis is divided into 4 stages: heating to 20 ℃ in one section, and keeping the temperature for 5 hours; heating the second stage to 30 ℃, and preserving the heat for 3 hours; heating the third section to 42 ℃, and preserving the heat for 5 hours; and raising the temperature to 55 ℃ in the fourth section, and keeping the temperature for 3 hours.
The mass ratio of the p-toluidine to the anhydrous hydrogen fluoride is 1: 3.
The mass ratio of the sodium nitrite to the p-toluidine is 0.7: 1.
The temperature for cooling is 10-20 ℃.
The purity of the p-fluorotoluene prepared by the method can reach 99.2 percent, and the yield can reach 97.3 percent.
Claims (8)
1. The preparation method of p-fluorotoluene is characterized by comprising the following steps:
reducing the anhydrous hydrogen fluoride to 0-5 ℃, slowly dropwise adding p-toluidine at the temperature of not more than 20 ℃, adding sodium nitrite after the dissolution is finished, and keeping the temperature at 0-5 ℃ for 1 h; then entering a pyrolysis stage; after pyrolysis, preserving heat for 2-3h, cooling, separating out an organic phase, and neutralizing with sodium carbonate until the pH is = 7-8; distilling to obtain p-fluorotoluene;
the pyrolysis is divided into 4 stages: heating to 20 ℃ in one section, and keeping the temperature for 4-5 h; heating to 30-35 ℃ in the second stage, and preserving heat for 3-4 h; heating to 40-43 deg.C in three stages, and keeping the temperature for 4-5 h; and heating to 50-55 ℃ in the fourth section, and preserving heat for 2-3 h.
2. The preparation method according to claim 1, wherein the pyrolysis stage is heating to 20 ℃ and keeping the temperature for 5 hours; the second stage of pyrolysis is heating to 30 ℃, and keeping the temperature for 3 hours; the temperature of the pyrolysis three sections is preferably raised to 42 ℃, and the temperature is kept for 5 hours; the temperature of the four pyrolysis stages is preferably raised to 55 ℃, and the temperature is kept for 3 h.
3. The method according to claim 1, wherein the mass ratio of p-toluidine to anhydrous hydrogen fluoride is 1 (2.8-3).
4. The method according to claim 3, wherein the mass ratio of p-toluidine to anhydrous hydrogen fluoride is 1: 3.
5. The production method according to claim 1, wherein the mass ratio of the sodium nitrite to the p-toluidine is (0.6 to 0.8): 1.
6. the production method according to claim 5, wherein the mass ratio of the sodium nitrite to the p-toluidine is 0.7: 1.
7. The method according to claim 1, wherein the cooling temperature is 10-20 ℃.
8. The method according to claim 1, wherein at least two times of liquid separation are required in the liquid separation process.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111269082A (en) * | 2020-02-20 | 2020-06-12 | 阜新宇泽化工有限公司 | Preparation method of 3, 5-dimethyl fluorobenzene |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111269082A (en) * | 2020-02-20 | 2020-06-12 | 阜新宇泽化工有限公司 | Preparation method of 3, 5-dimethyl fluorobenzene |
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